<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
   <div id="app">
       {{msg}}<input type="text" v-model.number="msg">
   </div>
</body>
</html>
<script src="./vue.js"></script>
<script>
   new Vue({
       el:'#app',
       data(){
           return{
               msg:''
           }
       },
       mounted:{}
   })
</script>